1. Field of the Invention
Embodiments of the invention relate to a semiconductor device and a method for fabricating the semiconductor device. In particular, embodiments of the invention relate to a semiconductor device comprising a multilayer dielectric film and a method for fabricating the semiconductor device.
2. Description of the Related Art
The degree of integration of semiconductor devices has increased in recent years. Accordingly, the respective amounts of chip area available for components of semiconductor devices have been reduced. A capacitor, which is used to store information in a DRAM device, is one such component, and capacitors that fit in the reduced area and that each have a capacitance that is the same as or greater than the capacitance of a capacitor fitting in a larger area are needed.
Thus, a dielectric film having a relatively high dielectric constant is desired in order to produce a capacitor including the dielectric film that has a desirable capacitance. Examples of dielectric films having relatively high dielectric constants include high-dielectric films such as zirconium oxide films (ZrO2 layer), tantalum oxide layers (Ta2O5 layer), or hafnium oxide films (HfO2 layer).
Even though a zirconium oxide single film has a relatively high dielectric constant in a crystalline state, a zirconium oxide single film will incur oxidation of a lower electrode due to diffusion of oxygen. Also, the heat generated during a subsequent process will reduce the dielectric constant and degrade the leakage current characteristics of a zirconium oxide single film. A tantalum oxide layer has a relatively high dielectric constant in a crystalline state; however, a high temperature heat treatment at a temperature of 700° C. or more needs to be performed on the tantalum oxide layer, and the high temperature heat treatment increases the leakage current of a capacitor including the tantalum oxide layer. Compared to a zirconium oxide film, hafnium oxide film is more resistant to diffusion of oxygen and has better heat resistance, but a hafnium oxide film in an amorphous state has a lower dielectric constant than a zirconium oxide film. A tetragonal system hafnium oxide has a higher dielectric constant than a zirconium oxide film; however, it is undesirable to use a hafnium oxide in a tetragonal system crystalline state to fabricate a dielectric film of a semiconductor device because it is difficult to shape a hafnium oxide in a tetragonal system crystalline state into a thin film.